Lately, there are many video cameras and stiff video cameras that have a solid-state image sensor at the image plane. In such a camera having a solid-state image sensor, an imaging lens is required that has different characteristics from those imaging lenses used with cameras employing silver chloride film.
On the other hand, as an imaging lens for a camera loaded with a solid-state image sensor, a compact lens having two lens groups is known that focuses by shifting only a rear lens group, as disclosed in Japanese Laid-Open Patent Application H09-197266. The overall length of the imaging lens remains constant during focusing. Also, the lens is a retro-focus type lens, being capable of providing a wide-angle view. Moreover, since it has a structure whereby a shutter mechanism does not move axially relative to an image formation surface, there is the advantage in that the shutter mechanism can be simplified. However, the lens of the above-noted laid-open patent application has either a six lens element or five lens element structure. With six lens elements, the overall lens length is too long. With five lens elements, an aspherical surface is used, thereby increasing the cost. Thus, such a lens has not satisfied the demand for a compact lens having a low cost of production. Moreover, the lens of the above-mentioned laid-open patent application has a large distortion and thus is not suitable for use in recording images of letters or other text documents and the like. Thus, there remains an unsatisfied demand for a low cost, wide-angle lens having minimum distortion.